People need to wear a mask or other PPE when they work in dangerous areas for the sake of safety. For example, a firefighter must wear a Self-Contained Breathing Apparatus (SCBA) when battling a fire. When a mask or PPE is worn, it becomes difficult to conduct face-to-face or person-to-radio communications because speech is heavily attenuated by the mask or PPE. What is more, any communication can be severely degraded by the background noise. In an extremely noisy environment, the radio can hardly pick up any clean speech at all. The firefighter has to shout loudly in order to be heard accurately. However, it is very important and necessary for people with a mask or PPE to have very clear and effective communications in such a high-noise environment. Poor communication not only decreases the working efficiency but also can be fatal.
So far, various solutions to improve the efficiency of communications have been developed and utilized. Operational procedures, such as hand and arm signals, provide a primitive solution and are not effective for scenarios requiring hands-free communications. Commercial Noise Cancellation Devices (NCDs) that can cancel ambient noise have been developed, although these devices can only work well when communicating without radios or when communicating through radios in a Push-To-Talk (PTT) mode. As a core component of these NCDs, three different kinds of microphones have been employed to improve the efficiencies of communications in the market: in-the-mask microphone, bond-conduct microphone, and adhesive microphone.
The first option, an in-the-mask microphone integrated with the mask, is an expensive solution since the first responder needs to replace the whole SCBA. The SCBA has a potential risk of air leakage because the microphone needs to be wired out for connection to an external radio. In addition, speech becomes distorted as it passes through the SCBA. The second option is the use of a bone-conduct microphone, but such a microphone needs to have a very tight contact with the human body. This contact needs to be either directly on the skull or the throat, which makes the user uncomfortable. The installation is clearly not stable since it cannot be rigidly fixed to the human body. An adhesive microphone attached to the outside of the SCBA is the third option. It cannot be considered a complete solution, however, due to the following reasons: (1) no further active noise reduction technology has been applied. As a result, the noise level is still not low enough for comfortable listening; (2) the speech picked up by the adhesive microphone sounds different from normal speech because the speech is excited within the SCBA, so the person who listens to the speech has difficulty in identifying who is talking; (4) it does not work with those first responders who don't wear a face mask but work in a high-noise environment.
Besides the above drawbacks, no present commercial NCD has adequately addressed the Voice Operates Switch (known as VOX) mode with radios. In VOX communication mode, the radio acts as an open microphone and sends signals out only when speech is detected. With these commercial NCDs, the VOX mode with radios is not robust enough against background noise, which may cause the radio to continuously transmit unwanted noise across the network and interfere with others' abilities to use the same frequency.
To address the above problems, a solution to improve communications is highly desirable. A NCD that supports both face-to-face and person-to-radio communications in highly noisy environments and addresses the above problems is presented with this invention. This device works effectively in high-noise environments through radios in PTT and VOX mode with and without radios.